Modular shelf system



FIG. 1 is a front perspective view of the modular shelf system showing my new design;

FIG. 2 is a rear perspective view thereof;

FIG. 3 is a front view thereof;

FIG. 4 is a top plan view thereof;

FIG. 5 is a side view thereof; and,

FIG. 6 is an in-use view thereof.

The broken lines in FIG. 6 are for environmental purposes only and form no part of the claimed design. 

I claim the ornamental design for a modular shelf system, as shown and described. 